Something seems off on geekbench score. My 8+ 256gb has single-core score of 4257 and multi-core score of 10604. Shouldn't your multi-core score be higher and not nearly 10% lower. I would recommend waiting day or two so phone can finish what ever it is doing that is related to initial setup and then run it again. I think you should see improvement then.
Was referring to geekbench multicore scoreThis was my iPhone X 256gb.
Seems about right to me.
Here is the new multi-score. Looks like it finished whatever it was doing.Remember, if you restored from backup, or recently setup your phone and downloaded apps, your phone has tasks in the background to optimize and pull down settings from the cloud, etc. Your benchmarks will likely be better in a day or two.